THE COMPONENT PRESSURE RECORDER. 



55 



is too great ; if less than half filled, the velocity is too small, etc. Two or more 

 inequality marks ai'e used to indicate a wide ditference from the mean condition. 

 By putting down a series of such readings measured at a number of revolutions 

 of the turn-table and taking a mean estimate, a very close approximation to the 

 soaring speed may be made, and the result has the weight of a very considerable 

 number of single readings. 



After completing the experiments of September 29 to October 9 according 

 to the plan laid out, the observations were reduced, and their discussion served 

 to show that additional experiments were needed to supplement them. There- 

 ixpon a second series was instituted for the purpose of obtaining additional data. 

 In this series the following five planes were used : 



The principal further objects to be attained were to determine with gi*eater 

 precision the soaring speeds of the 24 x 6 and 30 x 4.8 inch planes at small angles 

 and the horizontal pressure at those speeds ; to determine the soaring speed for 

 angles of the plane above 30°, so as to get the minimum point in the soaring 

 speed curve — that is, to determine the angle at which soaring takes place with 

 minimum velocity; and to ascertain the effect of size of plane on soaring speed 

 by adding to the planes previously used two of smaller size, viz., 12x6 inches 

 and 6x6 inches, having a cori-esponding diminution of weight. The five planes, 

 therefore, all have sizes and weights in the proportion of 500 grammes to the 

 square foot* (or 5,382 grammes to the square meter), and their soaring speeds are 

 entirely comparable for indicating the relative effect of shape and size. The new 

 observations were carried out on November 25, 26, December 5 and 11, and com- 

 prised over 80 individual experiments. Tlie detailed observations of both series 

 are presented in Tables XIV and XV, placed at the end of this chapter. 



The column headed " description of planes" gives the dimensions and weight 

 of the planes. The aspect of the plane — i. <?., its position with respect to the 



* The square foot -svas adopted as a unit in the earliest experiments, and its use has been continued as a 

 matter of experimental convenience, owing to considerations bearing,' upon the uniformity of apparatus. Were 

 these experiments to be recommenced, I should prefer to use C. G. S. (or at least metric) units throughout. 



